This invention relates to a memory arrangement for use in an information processor.
As is well known in the art, an information processor comprises a main memory for storing a great deal of information indicative of data and instructions, and a processing unit for processing the information in accordance with a program. The main memory has a predetermined access time while the processing unit, a prescribed operation time. The access time is remarkably longer than the operation time because of a huge capacity of the main memory. In other words, a time difference exists between the access time and the operation time. In order to raise throughput of a whole of the information processor, it is necessary to effectively reduce the time difference.
For this purpose, C. J. Conti has proposed an information processor comprising as a memory arrangement a high speed buffer memory between a main memory and a processing unit, in "CONCEPTS FOR BUFFER STORAGE" published March 1969 by International Business Machines Corporation. With the proposed information processor, a reduction of the time difference is possible only when the information to be accessed is stored in the memory arrangement. Otherwise, the reduction can not be expected. It is readily understood from this fact that the reduction of the time difference is accomplished by increasing a hit ratio representative of a probability that the information in question is present in the memory arrangement. In order to raise the hit ratio, the proposed information processor has utilized the fact that information accessed once by a program tends to be repeatedly accessed together with the neighboring information.
It is to be mentioned here that such a memory arrangement is automatically loaded with information by the use of hardware regardless of control by a program. Stated otherwise, the memory arrangement can not be managed by a programmer. In this sense, the memory arrangement is often called a cache memory.
On the other hand, it often happens that a programmer knows specific information temporarily but frequently used in a program. In this case, a memory arrangement is desirable which is operable as a local memory wherein such specific information is located. By the use of the local memory, the specific information might rapidly be derived from the local memory rather than from the main memory. Improvement of throughput of the information processor might therefore be accomplished because the main memory is not accessed.
However, a conventional information processor practically carries out control operation such that a programmer does not need to pay attention to a state of the memory arrangement in order to save labor of the programmer. As a result, the conventional information processor is disadvantageous in that the programmer can not positively and intentionally utilize the buffer memory. Thus, the improvement of the throughput can not be expected with the conventional information processor even when the programmer knows the specific information.